Active stylus synchronization with multiple communication protocols

Abstract

An active stylus includes a stylus electrode configured to electrostatically couple with one or more electrodes of a display device having a capacitance-based touch sensor, transmit logic configured to drive the stylus electrode with a synchronization waveform that is configured, via interpreting a response on one or more electrodes of a first display device, to enable the first display device to become time synchronized with the active stylus in a stylus-initiated synchronization mode, receive logic configured to interpret a response on the stylus electrode caused by a synchronization waveform being driven on one or more electrodes of a second display device, to enable the active stylus to become time synchronized with the second display device in a display-initiated synchronization mode, and a controller configured, in response to detection of a condition, to cause the active stylus to switch from one of the synchronization modes to the other.

The invention claimed is: 
     
       1. An active stylus for use with one or more touch-sensitive display devices, comprising:
 a stylus electrode configured to electrostatically couple with one or more electrodes of a display device having a capacitance-based touch sensor; 
 transmit logic configured to drive the stylus electrode with a first synchronization waveform that is configured, via interpreting a response on one or more electrodes of a first display device, to enable the first display device to become time synchronized with the active stylus, where the first synchronization waveform is driven on the stylus electrode as part of a first repeated touch-sensing frame, this mechanism of synchronization being referred to as a stylus-initiated synchronization mode; 
 receive logic configured to interpret a response on the stylus electrode caused by a second synchronization waveform being driven on one or more electrodes of a second display device, such interpretation configured to enable the active stylus to become time synchronized with the second display device, where the second synchronization waveform is driven on the one or more electrodes of the second display device as part of a second repeated touch-sensing frame that is arranged differently than the first repeated touch-sensing frame, this mechanism of synchronization being referred to as a display-initiated synchronization mode; and 
 a controller configured, in response to detection of a condition, to cause the active stylus to switch from one of the synchronization modes to the other. 
 
     
     
       2. The active stylus of  claim 1 , wherein detecting the condition includes, while operating in the stylus-initiated synchronization mode, receiving the second synchronization waveform from the second display device. 
     
     
       3. The active stylus of  claim 1 , wherein detecting the condition includes, while operating in the stylus-initiated synchronization mode, determining that the active stylus is less than a threshold distance from the second display device. 
     
     
       4. The active stylus of  claim 1 , wherein detecting the condition includes, while operating in the display-initiated synchronization mode, determining that the active stylus is greater than a threshold distance from the second display device. 
     
     
       5. The active stylus of  claim 1 , wherein the stylus-initiated synchronization mode is a default mode of operation of the active stylus, and wherein the controller is configured to cause the active stylus to switch to operation in the display-initiated synchronization mode in response to receiving the second synchronization waveform from the second display device or determining that the active stylus is less than a threshold distance from the second display device. 
     
     
       6. The active stylus of  claim 5 , wherein the active stylus is configured to not drive the stylus electrode with the first synchronization waveform of the stylus-initiated synchronization mode while operating in the display-initiated synchronization mode. 
     
     
       7. The active stylus of  claim 1 , wherein the second synchronization waveform driven on the one or more electrodes of the second display device in the display-initiated synchronization mode is different than the first synchronization waveform driven on the one or more electrodes of the first display device in stylus-initiated synchronization mode. 
     
     
       8. The active stylus of  claim 1 , wherein the receive logic is configured to interpret the response on the stylus electrode caused by the second synchronization waveform being driven on one or more electrodes of the second display device, when the stylus electrode is not being driven by the transmit logic. 
     
     
       9. The active stylus of  claim 1 , wherein the receive logic is configured to enable the active stylus to become time synchronized with any of a plurality of display devices having capacitance-based touch sensors by interpreting different responses on the stylus electrode caused by different synchronization waveforms corresponding to different ones of the plurality of different display devices. 
     
     
       10. A method for operating an active stylus for use with one or more touch-sensitive display devices, the method comprising:
 driving a stylus electrode of the active stylus with a stylus-initiated synchronization waveform as part of a first repeated touch-sensing frame, the stylus-initiated synchronization waveform being configured to enable, via capacitive coupling with one or more electrodes of a capacitance-based touch sensor of a first display device, the first display device to become time synchronized with the active stylus, such synchronization mechanism being referred to as a stylus-initiated synchronization mode; 
 receiving, on the stylus electrode, a response caused by a display-initiated synchronization waveform driven on one or more electrodes of a capacitance-based touch sensor of a second display device as part of a second repeated touch-sensing frame that is arranged differently than the first repeated touch-sensing frame; and 
 interpreting the response on the stylus electrode to cause the active stylus to become time synchronized with the second display device, such synchronization mechanism being referred to as a display-initiated synchronization mode. 
 
     
     
       11. The method of  claim 10 , further comprising:
 subsequent to the active stylus becoming time synchronized with the second display device, driving the stylus electrode with the stylus-initiated synchronization waveform based on detection of a condition. 
 
     
     
       12. The method of  claim 11 , wherein detecting the condition includes not receiving an expected response on the stylus electrode from the second display device for greater than a threshold duration. 
     
     
       13. The method of  claim 12 , wherein the stylus electrode is not driven by the stylus-initiated synchronization waveform while the active stylus is time synchronized with the second display device if the expected response is received on the stylus electrode from the second display device within the threshold duration. 
     
     
       14. The method of  claim 10 , wherein the response from the second display device is received on the stylus electrode when the stylus electrode is not being driven with the stylus-initiated synchronization waveform. 
     
     
       15. An active stylus for use with one or more touch-sensitive display devices, comprising:
 a stylus electrode configured to electrostatically couple with one or more electrodes of a display device having a capacitance-based touch sensor; 
 transmit logic configured to drive the stylus electrode with a first synchronization waveform that is configured, via interpreting a response on one or more electrodes of a first display device, to enable the first display device to become time synchronized with the active stylus, where the first synchronization waveform is driven on the stylus electrode as part of a first repeated touch-sensing frame, this mechanism of synchronization being referred to as a stylus-initiated synchronization mode; 
 receive logic configured to interpret a response on the stylus electrode caused by a second synchronization waveform being driven on one or more electrodes of a second display device, such interpretation configured to enable the active stylus to become time synchronized with the second display device, where the second synchronization waveform is driven on the one or more electrodes of the second display device as part of a second repeated touch-sensing frame that is arranged differently than the first repeated touch-sensing frame, this mechanism of synchronization being referred to as a display-initiated synchronization mode; and 
 a controller configured to cause the active stylus to operate in the stylus-initiated synchronization mode as a default mode of operation of the active stylus, and wherein the controller is configured to cause the active stylus to switch to operation in the display-initiated synchronization mode in response to receiving the second synchronization waveform from the second display device or determining that active stylus is less than a threshold distance from the second display device. 
 
     
     
       16. The active stylus of  claim 15 , wherein the transmit logic is configured to not drive the stylus electrode with the first synchronization waveform of the stylus-initiated synchronization mode while operating in the display-initiated synchronization mode. 
     
     
       17. The active stylus of  claim 15 , wherein the controller is configured, subsequent to the active stylus becoming time synchronized with the second display device, to cause the active stylus to switch to operation in the stylus-initiated synchronization mode in which the stylus electrode is driven with the first synchronization waveform based on the transmit logic not receiving an expected response on the stylus electrode from the second display device for greater than a threshold duration. 
     
     
       18. The active stylus of  claim 15 , wherein the second synchronization waveform driven on the one or more electrodes of the second display device in the display-initiated synchronization mode is different than the first synchronization waveform driven on the one or more electrodes of the first display device in stylus-initiated synchronization mode.